Multiformat transmitter

Abstract

Methods and apparatus for supporting a plurality of modulation formats using a single transmitter are disclosed. According to one aspect of the present invention, a transmitter arrangement that provides a signal to a modulator that creates an optical data stream from the signal includes an encoder and a switching/filtering arrangement. The encoder has a state that is varied between first and second encoder states. If the state is the first encoder state, the encoder encodes the signal in a format associated with an optical duobinary (ODB) modulation format. Otherwise, the encoder does not encode the signal in the format associated with the ODB modulation format. The switching/filtering arrangement receives the signal from the encoder, and provides the signal to the modulator. If the variable state of the encoder is the first encoder state, the switching/filtering arrangement has a low bandpass configuration. Otherwise, the switching/filtering arrangement has a high bandpass configuration.

1. A transmitter arrangement, the transmitter arrangement being arranged to provide a signal to a modulator, the modulator being arranged to create an optical data stream from the signal, the transmitter arrangement comprising:
 an encoder, the encoder having a variable state, the variable state of the encoder being arranged to be varied between a first encoder state and a second encoder state, wherein if the variable state of the encoder is the first encoder state, the encoder encodes the signal in a format associated with an optical duobinary (ODB) modulation format, and wherein if the variable state of the encoder is the second state, the encoder does not encode the signal in the format associated with the ODB modulation format; and 
 a switching/filtering arrangement, the switching/filtering arrangement being arranged to be varied between a low bandpass configuration and a high bandpass configuration, the switching/filtering arrangement further being arranged to receive the signal from the encoder and to provide the signal to the modulator, wherein if the variable state of the encoder is the first encoder state, the switching/filtering arrangement is arranged in the low bandpass configuration, and wherein if the variable state of the encoder is the second encoder state, the switching/filtering arrangement is arranged in the high bandpass configuration. 
 
   
   
     2. The transmitter arrangement of  claim 1  wherein the switching/filtering arrangement includes two radio frequency (RF) switches and a fixed low-bandwidth/low-pass filter, the two RF switches being arranged to route the signal through the filter, if an ODB mode for the two RF switches has been selected, or not to route the signal through the filter, if a non-return to zero (NRZ) mode for the two RF switches has been selected. 
   
   
     3. The transmitter arrangement of  claim 1 , wherein the switching/filtering arrangement is a variable filter, and wherein the low bandpass configuration is a low bandpass filter configuration and the high bandpass configuration is a high bandpass filter configuration. 
   
   
     4. The transmitter arrangement of  claim 3  wherein the low bandpass configuration is an ODB configuration and the high bandpass configuration is a non-return to zero (NRZ) configuration. 
   
   
     5. The transmitter arrangement of  claim 3  wherein the variable filter includes micro stripe filters and variable capacitance diodes. 
   
   
     6. The transmitter arrangement of  claim 3  further including:
 a variable driver arrangement, the variable driver arrangement being arranged to apply a drive voltage to the signal, the drive voltage having a first value when the variable state of the encoder is the first encoder state and a second value when variable state of the encoder is the second encoder state, the variable driver arrangement further being arranged to obtain the signal from the encoder and to provide the signal to the variable filter. 
 
   
   
     7. The transmitter arrangement of  claim 6  further including:
 a controller arrangement, the controller arrangement being arranged to vary the variable state of the encoder and an output voltage of the driver, the controller arrangement further being arranged to select between the low bandpass filter configuration and the high bandpass filter configuration. 
 
   
   
     8. The transmitter arrangement of  claim 3  wherein when a chromatic dispersion total residual associated with the signal has a magnitude of less than approximately 1000 ps/nm, the variable filter is arranged in the high bandpass filter configuration and the signal is in a format associated with a non-return to zero (NRZ) modulation format. 
   
   
     9. The transmitter arrangement of  claim 3  wherein when a chromatic dispersion total residual associated with the signal has a magnitude of greater than approximately 1000 ps/nm, the variable filter is arranged in the low bandpass filter configuration and the signal is in the format associated with the ODB modulation format. 
   
   
     10. The transmitter arrangement of  claim 3  wherein the variable filter includes a varactor diode. 
   
   
     11. A transmitter arrangement, the transmitter arrangement being arranged to provide a signal to a modulator, the modulator being arranged to create an optical data stream from the signal, the transmitter arrangement comprising:
 means for encoding the signal in a format associated with an optical duobinary (ODB) modulation format, the means for encoding the signal having a first state and a second state, wherein the first state is associated with the ODB modulation format and wherein the second associated is not associated with the ODB modulation format; 
 means for alternating between first state and the second state; and 
 means for alternating between a low bandpass configuration and a high bandpass configuration, the means for alternating between the low bandpass configuration and the high bandpass configuration including means for receiving the signal from the means for encoding the signal, the means for alternating between the low bandpass configuration and the high bandpass configuration further including means for providing the signal to the modulator, wherein the low bandpass configuration is in effect if the means for encoding is in the first state and the high bandpass configuration is in effect if the means for encoding is in the second state. 
 
   
   
     12. A method for providing a non-optical signal to a modulator, the modulator being arranged to create an optical data stream from the signal, the method comprising:
 determining if the signal is to be encoded in a format associated with an optical duobinary (ODB) modulation format; 
 encoding the signal in the format associated with the ODB format if it is determined that the signal is to be encoded in the format associated with the ODB format; 
 applying a drive voltage to the signal, wherein if the signal is encoded in the format associated with the ODB format, the drive voltage has a first value and wherein if the signal is not encoded in the format associated with the ODB format, the drive voltage has a second value; and 
 determining a bandwidth of the signal to be provided to the modulator, wherein determining the bandwidth of the signal to be provided to the modulator includes providing a first bandwidth associated with the signal to the modulator if the signal is encoded in the format associated with the ODB format and providing a second bandwidth associated with the signal to the modulator if the signal is not encoded in the format associated with the ODB format. 
 
   
   
     13. The method of  claim 12  wherein the signal is associated with an approximately 10 Gb/s transmission system and wherein the first bandwidth has a magnitude of approximately three GigaHertz, and the second bandwidth has a magnitude of approximately ten GHz. 
   
   
     14. The method of  claim 12  further including providing the signal to a variable filter, wherein the variable filter determines the bandwidth of the signal to be provided to the modulator. 
   
   
     15. The method of  claim 12  further including providing the signal to a radio frequency (RF) switch arrangement. 
   
   
     16. The method of  claim 15  wherein the RF switch arrangement includes at least a low bandwidth filter. 
   
   
     17. The method of  claim 16  wherein the RF switch arrangement also includes a high bandwidth filter, and wherein outputs of the low bandwidth filter and the high bandwidth filter outputs are provided to a second RF switch. 
   
   
     18. The method of  claim 17  wherein the RF switch output of the second RF switch is provided to an optical modulator. 
   
   
     19. A method of creating an optical signal from an electrical signal, the method comprising:
 providing the electrical signal as an input to a selective transmission format block, the selective transmission format block being arranged to create an optical signal in a format associated with an optical duobinary (ODB) format and an optical signal in a format associated with a non-return-to-zero (NRZ) format, wherein the selective transmission format block is arranged to select one from the group including the electrical signal in the format associated with the ODB format and the electrical signal in the format associated with the NRZ format; 
 providing the selected electrical signal from the selective transmission format block to a modulator; and 
 creating an optical signal from the selected electrical signal. 
 
   
   
     20. A line card suitable for creating an optical signal from an electrical signal, the line card comprising:
 a selective transmission format block, the selective transmission format block being arranged to receive an electrical input signal, the selective transmission format block further being arranged to create signals of a plurality of formats from the electrical input signal, the plurality of formats including a first format associated with an optical duobinary (ODB) format and a second format associated with a non-return-to-zero (NRZ) format, wherein the selective transmission format block derives an electrical output signal from the electrical input signal, selecting from the group which includes the first format and the second format; and 
 a modulator, the modulator being arranged to convert the electrical output signal into an optical signal.